The present invention relates to applications of a spatial light modulator that employs an array of micro mirrors represented by a digital micro-mirror device (DMD), and more particularly to an illuminating-light controller, such as a projector with a plurality of light sources, etc., and an illuminating-light control method.
There has recently been an ever-increasing demand for large-screen display devices for the display of images and monitoring, such as personal computers (PCs), televisions, etc. Projection type displays, which are three-panel type projectors using three light valves (liquid crystal panels), have rapidly spread in use because they are higher in luminance and smaller in size, lighter in weight, and lower in cost, compared with projection type displays using CRTs, which were conventionally the trend. However, the light valve is expensive, and a projector using three expensive light valves becomes very high in cost as a whole. Furthermore, this type of projector has an increased size because of the optical system is complicated.
On the other hand, a color-sequential display type has been provided in which a high-speed light valve is used. Light with three primary colors is sequentially projected at high speeds, having field images with each color are displayed in sequence. Full color frames are displayed by exploiting an afterimage on the eye. FIG. 10 is a diagram showing the rough schematic drawing of a color-sequence display type of projector employing a digital micro mirror device as a light valve. First, white light emitted from a light source 201 is converted to parallel light by a reflecting mirror 202 and is directed to a rotary color filter disc 204 through a condenser lens 203. The light beam with three primary colors, red (R), green (G), and blue (B), generated by the rotary color filter disc 204, is irradiated to a light valve 207 through a coupling lens 205 and a mirror 206. The light valve 207 employs a DMD for changing the direction of reflected light by controlling the inclination of a micro mirror that is a reflecting surface. The light, irradiated by the light valve 207 tilted when it is in an ON state, is incident on a projection lens 208 and projected on a screen (not shown).
FIG. 11 is a diagram showing the operational principles of the DMD employed as the light valve 207. The white light emitted from the light source 201 is reflected by the micro mirror 209 and incident on the projection lens 208. The micro mirror 209 is constructed to tilt about 10 degrees clockwise or counterclockwise. When the micro mirror 209 is in an ON state indicated by a solid line in FIG. 11, the reflected light is incident on the projection lens 208. When it is in an OFF state indicated by a broken line, the reflected light is not incident on the projection lens 208. Thus, by controlling the time of the ON state or OFF state in which the micro mirror 209 tilts, it is possible to adjust the quantity of light projected. As a result, light modulation can be performed.
FIG. 12 is a diagram for explaining the timing at which a color-sequence display type is performed. As shown in the upper part of FIG. 12, for the illuminating light passed through the rotary color filter disc 204, R-, G-, and B-fields are repeatedly outputted for each frame as time goes by. The light valve 207 controls the ON-state of the micro mirror 209, based on input video data. For example, the light valve 207 operates so that illuminating light is incident on the projection lens 208 only for a period indicated by a solid line in the intermediate part of FIG. 12. As a result, R-, G-, and B-images are optically modulated and sequentially displayed. This color-field sequential type of projector (hereinafter called a single-panel type projector) is smaller in size, lighter in weight, and lower in cost, compared with a liquid crystal type of projector using three light valves, for instance, and is widely being used as a portable projector of small size for business.
For example, Published Unexamined Patent Application No. 10-153755 discloses a technique wherein, in order to vary and output the polarizing angles of respective projected images for the left and right eyes, light from a white light source is focused on a rotary polarizing color filter, the light serially modulated in the order of R, G, and B through the color filter is directed to a DMD, and the reflected light modulated to an image corresponding to each color by the DMD is projected on a screen by a projection lens. In the technique disclosed in such a publication, however, brightness is perceptibly reduced by polarization and sufficient luminance cannot be obtained. In addition, because a polarizing panel that rotates at high speeds is employed, the polarizing surface will tilt and that lateral separation will become unsatisfactory.
The present invention has been made in order to solve the aforementioned problems. Accordingly, it is an object of the present invention to eliminate loss due to a coupling optics, for superposing lights, even when using a plurality of lamps, and to ensure approximately twice as much brightness.
A first feature of the present invention includes an illuminating-light controller comprising a light modulator for projecting light on a corresponding area by tilting a reflecting surface. A first light source emits a first light that is projected on the corresponding area by illuminating the first light to the reflecting surface of the spatial light modulator being tilted at a first angle. A second light source for emits a second light that is projected on the corresponding area by illuminating the second light to the reflecting surface of the light modulator being tilted at a second angle. Still further included is a control section for controlling the first light emitted from the first light source and the second light emitted from said second light source.
Another feature of the present invention includes an illuminating-light controller comprising a micro mirror type spatial light modulator to project light, emitted from a light source, on a corresponding area by tilting a reflecting surface. A first light source emits a first light, which is projected on the corresponding area, by illuminating the first light to the reflecting surface of the spatial light modulator tilted at a first angle. A second light source emits a second light, which is projected on the corresponding area, by illuminating the second light to the reflecting surface of the spatial light modulator tilted at a second angle. Finally, a control section controls the first light emitted from the first light source and the second light emitted from the second light source.
In accordance with another important aspect of the invention, there is provided a projector comprising a first light source to emit light in pulse form, and a second light source to emit light in pulse form. The first light source and the second light source are switched alternately. A spatial light modulator is equipped with a micro mirror being tiltable to a first angle and then to a second angle. The light modulation is performed by the tilting of the micro mirror. A projection lens receives incident light reflected by the micro mirror of the spatial light modulator. Further aspects of the invention include a control section for controlling the first light source so that the light emitted from the first light source is modulated and directed to the projection lens when the micro mirror is tilted at the first angle, and for controlling the second light source so that the light emitted from the second light source is modulated and directed to the projection lens when the micro mirror is tilted at the second angle.